1. Field of the Art
The present invention relates to production of organic acids by a biological technique. More particularly, the present invention relates to conversion of nitrile compounds into the corresponding organic or carboxylic acids by the action of microorganisms.
Organic or carboxylic acids are utilized as materials for producing various chemicals, and it is known that acrylic acid and methacrylic acid, in particular, are important as materials for, e.g. polymeric products and nicotinic acid is important for use in medicines.
2. Related Art and the Problems Inherent Therein
Known in the art for converting nitrile compounds into the corresponding acids are chemical synthesis technique and biological technique. The chemical synthesis may entail the problem of disposal of wastes resulting from the synthesis in which a strong mineral acid is used for hydrolyzing the nitrile. The biological technique, on the other hand, is advantageous in that an enzyme inherent in microorganism is used as the hydrolysis catalyst whereby the acid is obtainable under mild conditions.
Examples of the biological technique may include those where use is made as the microorganism of Bacillus, Bacteridium, Micrococcus, and Brevibacterium as set forth in U.S. Pat. No. 3,940,316, of Acinetobacter as set forth in Japanese Patent Publication No. 2596/1988, of Corynebacterium as set forth in Japanese Patent Publication No. 56800/1988, and of Alcaligenes as set forth in Japanese Patent Laid-Open Publication No. 132392/1989.
The first group of microorganisms as set forth in U.S. Pat. No. 3,940,316 do not appear to us to be equipped with high activity so that the process can be held practical.
In view of this, an improvement has been produced, in e.g. Japanese Patent Publication No. 2596/1988, loc. cit, to enhance the catalyst activity of the microorganisms, which comprises culturing a microbial strain in the presence of a nitrile compound added as an inducer of the hydrolysis enzyme. This improvement may, however, entail a problem such that the microorganism utilizes the nitrile compound added to the culture medium during the culturing and it is required to supplement the nitrile consumed whereby it may be difficult to maintain the microorganism at the highest activity level possible when the operation is conducted in a commercial scale. It may be another problem that the activity so obtained is not very satisfactory.